Olefin polymerization catalyst having a multidentate ligand

Abstract: Disclosed is an olefin polymerization catalyst comprising a transition metal selected from metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the Periodic Table of the Elements, and ligands L 1 and L 2 bonded thereto, wherein ligand L 1 is a trispyrazolyl tridentate ligand and ligand L 2 is an alkapolyenyl ligand, and wherein L 1 contains an element of Group VB or Group VIB. The catalyst of the present invention has extremely high catalytic activity for an olefin polymerization reaction as compared to conventional olefin polymerization catalysts.

Description: BACKGROUND OF THE INVENTION Field of The Invention The present invention relates to an olefin polymerization catalyst having a multidentate ligand. More particularly, the present invention is concerned with an olefin polymerization catalyst comprising at least one transition metal compound selected from compounds of formulae I and II: and wherein M is a transition metal selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the Periodic Table of the Elements; X is an anionic ligand; n is an integer represented by formula G-2 in which G is the Group number of the Group of the Periodic Table to which the transition metal belongs; J is a non-coordinating anion; ligand L 1 is a trispyrazolyl tridentate ligand; and ligand L 2 is an alkapolyenyl ligand having a σ-bond and two or more π-bonds, wherein L 1 contains an element of Group VB or Group VIB of the Periodic Table of the Elements. The catalyst of the present invention has extremely high catalytic activity for an olefin polymerization reaction as compared to conventional olefin polymerization catalysts. Therefore, by the use of the catalyst of the present invention, a desired olefin polymer can be produced efficiently with a high productivity per unit weight of the catalyst. The olefin polymerization catalyst of the present invention is also advantageous in that it has high heat stability, that the olefin polymer produced has high molecular weight, high bulk density and improved powder characteristics, and that the molecular weight of the olefin polymer can be controlled and the amount of an auxiliary catalyst which is optionally employed can be reduced. This application is a divisional of European patent application no. 94200736.0. Discussion of Related Art In the polymerization of an olefin, it is known to employ as a catalyst a compound having a monodentate ligand comprised of nitrogen as a heteroatom and having a single alkadienyl ligand. For example, Journal "Organometallics" 9 , 867 (1990) discloses the polymerization of an olefin in which use is made of a catalyst comprised of a metal of Group IIIA of the Periodic Table in which the catalyst has a heteroatom monodentate ligand and, bridge-bonded thereto, an alkadienyl ligand. Unexamined Japanese Patent Application Laid-Open Specification No. H3-163088 (corresponding to European Patent Application Publication No. 416815) discloses the polymerization of an olefin in which use is made of a catalyst comprised of a transition metal in which the catalyst has a ligand containing no π-bond and, bridge-bonded thereto, a single ligand having at least one delocalized π-bond, and a formula shown in this Japanese patent document indicates that the ligand containing no π bond is a monodentate ligand. Further, Unexamined Japanese Patent Application Laid-Open Specification No. H3-188092 (corresponding to European Patent Application Publication No. 420436 and U.S. Patent No. 5,055,438) discloses the polymerization of an olefin in which use is made of a catalyst comprised of a metal of Group IVA of the Periodic Table in which the catalyst has a heteroatom ligand and a cyclopentadienyl ligand, and a formula shown in this Japanese patent document indicates that the heteroatom ligand is a monodentate ligand. However, the catalytic activities of these conventional catalysts are extremely low. The catalyst disclosed in the above-mentioned Unexamined Japanese Patent Application Laid-Open Specification No. H3-163088 exhibits a relatively high catalytic activity, but even in the case of this catalyst, the catalytic activity is still unsatisfactory. Illustratively stated, in Working Example 1 of Unexamined Japanese Patent Application Laid-Open Specification No. H3-163088, an olefin polymerization reaction is performed using a catalyst having a monodentate nitrogen ligand and, bridge-bonded thereto, a cyclopentadienyl ligand in order to produce an atactic polypropylene, but the yield of the polymer produced is as small as less than 100 g/g of the metal of the catalyst per hour. Unexamined Japanese Patent Application Laid-Open Specification No. H1-95110 (corresponding to U.S. Patent No. 4,870,042) discloses the polymerization of an olefin, using as a catalyst a reaction product between an alkali metal salt of pyrazolyl borate (containing nitrogen as a heteroatom) and a halide of titanium or zirconium, and aluminoxane as an auxiliary catalyst. In Working Example 3 of the above-mentioned unexamined Japanese patent document No. H1-95110, polyethylene is produced using as a catalyst a reaction product between potassium hydrotrispyrazolyl borate and titanium chloride, but the catalyst is extremely low in catalytic activity, so that the yield of the polyethylene produced under a 1 atm. ethylene pressure is as small as less than 200 g/g of the metal of the catalyst per hour. Unexamined Japanese Patent Application Laid-Open Specification No. H4-305585 (corresponding to European Patent Application Publication No. 482934 and U.S. Patent No. 5,237,069) discloses a catalyst comprised of an organometallic compound having a hydrotris(pyrazolyl)borate ligand (containing nitrogen as a heteroatom) and an anionic ligand, and describes that examples of ligands do not include a functional cyclopentadienyl ligand. The catalyst of the above-mentioned unexamined Japanese patent document No. H4-305585 is improved in catalytic activity to some extent, but the yield of polystyrene produced using this catalyst is still as small as less than 4 kg/g of the metal of the catalyst per hour. EP-A-0 574 794 discloses an organometallic compound for use as a catalyst component for the polymerization of olefins, said compound comprising a transition metal of any one of group 3A to group 8 of the Periodic Table and at least one cyclic ligand containing a heteroatom of group 5A or group 5B of the Periodic Table which is capable of forming a π-bond, wherein said transition metal is bonded to the heterocyclic ligand via said heteroatom and a π-bond. WO 91/13074 disloses an olefin polymerization catalyst composition comprising a trivalent transition metal compound wherein two valencies of the transition metal are filled by bidentate chelating compounds, each of the bidentate chelating compounds having a combined hydrocarbyl constituency such that the trivalent transition metal compound is soluble in hydrocarbon solvents. In Journal of Organometallic Chemistry, Vol. 384 (1990), pages 271-278, organometallic compounds are disclosed which have 5-membered heterocyclic ligands each containing one heteroatom. In Journal of Organometallic Chemistry, Vol. 193 (1980), pages C13-16, organometallic compounds are described which have a 5-membered heterocyclic ligand. Another ligand of the respective compounds is a cyclopentadienyl ligand. Further, due to the low catalytic activity of the conventional catalysts which have a monodentate ligand containing nitrogen as a heteroatom or a tridentate ligand containing nitrogen as a heteroatom, such as a trispyrazole borate ligand, the conventional catalysts need to be used in a large amount, so that additional cumbersome operations are needed, such as deashing of an olefin polymer produced (i.e., removal of a catalyst from the olefin polymer produced). Therefore, the conventional olefin polymerization catalysts are unsatisfactory for use in commercially producing olefin polymers. SUMMARY OF THE INVENTION The present inventors have made extensive and intensive studies with a view toward developing a novel olefin polymerization catalyst which is free from the above-mentioned problems inevitably accompanying the conventional olefin polymerization catalysts which have a monodentate ligand containing nitrogen as a heteroatom or a tridentate ligand containing nitrogen as a heteroatom, such as a trispyrazolyl borate ligand. As a result, it has unexpectedly been found that a novel olefin polymerization catalyst comprising a transition metal selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the Periodic Table of the Elements, and ligands L 1 and L 2 bonded thereto, wherein the ligand L 1 is a trispyrazolyl borate tridentate ligand containing nitrogen as a heteroatom and the ligand L 2 is an alkapolyenyl ligand, such as a cyclopentadienyl ligand, exhibits extremely high catalytic activity for olefin polymerization. That is, the above-mentioned novel olefin polymerization catalyst having a specific multidentate ligand exhibits an extremely high catalytic activity for olefin polymerization, as compared to the conventional olefin polymerization catalysts which have a monodentate nitrogen ligand as a heteroatom or a tridentate ligand containing nitrogen as a heteroatom (such as a trispyrazolyl borate ligand) but have no alkapolyenyl ligand (such as a cyclopentadienyl ligand). Further, as compared to the conventional olefin polymerization catalysts, the above-mentioned novel catalyst of the present invention is also advantageous in that it has high heat stability, that an olefin polymer produced has a high molecular weight, high bulk density and improved powder characteristics, that the molecular weight of the olefin polymer can be controlled simply by adding hydrogen and that the amount of alkylaluminoxane as an auxiliary catalyst which may be optionally employed can be reduced. Furthermore, by virtue of the high catalytic activity of the above-mentioned novel catalyst, the amount of a catalyst to be used for an olefin polymerization can be largely reduced, so that there is no need for additional cumbersome operations, such as deashing of a produced olefin polymer (i.e., removal of a catalyst from the polymer). Based on these novel findings, the present invention has been completed. Accordingly, it is a primary object of the present invention to provide a novel olefin polymerization catalyst which is not only extremely high in catalytic activity but also renders it possible to produce an olefin polymer having a desired molecular weight and excellent properties. The foregoing and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and appended claims. DETAILED DESCRIPTION OF THE INVENTION According to the present invention, there is provided an olefin polymerization catalyst comprising at least one transition metal compound selected from compounds of formulae I and II: wherein: M is a transition metal selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the Periodic Table of the Elements, X is an anionic ligand, n is an integer represented by formula G-2 in which G is the Group number of the Group of the Periodic Table to which the transition metal belongs, and L 1 and L 2 are ligands defined below, wherein a bridge bond is optionally formed between L 1 and L 2 ; and wherein: M, X, n, L 1 and L 2 are as defined for formula (I), and J is a non-coordinating anion. Ligand L 1 is a trispyrazolyl tridentate ligand represented by formula III: wherein: A is a carbon atom, or a boron atom substituted with a substituent selected from the group consisting of: a hydrogen atom, a saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 -C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; each of Z 1 , Z 2 and Z 3 independently represents a pyrazolyl group represented by formula IV: wherein: each of R 3 , R 4 and R 5 independently represents: a hydrogen atom, a saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 -C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, wherein a bridge bond is optionally formed between R 3 and R 4 or between R 3 and R 5 , and ligand L 2 is an alkapolyenyl ligand having a σ-bond and two or more π-bonds. The "Periodic Table of the Elements" referred to herein is the Periodic Table of the Elements described in "Kagaku Binran (Chemistry Handbook)", the third revised edition, the fourth print, edited by the Chemical Society of Japan and published by Maruzen Co. Ltd., Japan. Accordingly, the "Groups" and "series" used herein are in accordance with the above-mentioned Periodic Table of the Elements. Examples of anionic ligand X in formulae (I) and (II) include a hydrogen atom; a halogen atom, such as a fluorine atom, a chlorine atom, a bromine atom or an iodine atom; a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 -C 14 aromatic hydrocarbon group or at least one halogen atom; a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom; an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 -C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 -C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom; a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 - C 10 aromatic hydrocarbon group, or at least one halogen atom. As illustrative examples of unsubstituted or substituted aliphatic and aromatic hydrocarbon groups employable as ligand X, there can be mentioned a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a cyclopentyl group, an isopentyl group, a neopentyl group, a hexyl group, a cyclohexyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, a pentadecyl group, a cyclohexenyl group, a cyclohexenylmethyl group, a norbornenyl group, a phenyl group, a tolyl group, an ethylphenyl group, a xylyl group, an isopropylphenyl group, a naphthyl group, a methylnaphthyl group, a biphenyl group, an anthracyl group, a benzyl group, a phenethyl group, a phenylpropyl group, a naphthylmethyl group, a trichloromethyl group, a trifluoromethyl group, a pentafluoroethyl group, a hexafluorocyclohexyl group, a chlorophenyl group, a hexafluorophenyl group, a chloronaphthyl group, a bromonaphthyl group, a p-trichloromethylphenyl group, a p-fluorophenylmethyl group, and a pentachlorobenzyl group. Illustrative examples of substituted oxy groups include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a hexyloxy group, a cyclohexyloxy group, a decyloxy group, a phenoxy group, a naphthoxy group, a tolyloxy group, a methylnaphthoxy group, a benzyloxy group, and a phenethyloxy group. Illustrative examples of substituted thio groups include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a hexylthio group, a cyclohexylthio group, a decylthio group, a phenylthio group, a naphthylthio group, a tolylthio group, and a methylnaphthylthio group. Illustrative examples of substituted silyl groups include a trimethylsilyl group, a triethylsilyl group, and a phenyldimethylsilyl group. Illustrative examples of substituted siloxy groups include trimethylsiloxy group, a triethylsiloxy group, and a phenyldimethylsiloxy group. Further examples of anionic ligand X in formulae (I) and (II) include an N,N-disubstituted amino group and a P,P-disubstituted phosphino group which are, respectively, represented by formulae (VII) and (VIII): -NR 2 and -PR 2 wherein each R is monovalent and independently represents a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group and wherein a bridge bond is optionally formed between the two Rs. Illustrative examples of N,N-disubstituted amino groups include a dimethylamino group, a diethylamino group, an ethylmethylamino group, a diisopropylamino group, a di(t-butyl)amino group, a dicyclohexylamino group, a diphenylamino group, a ditolylamino group, a pyrrolyl group, a pyrazolyl group, and an imidazolyl group. Illustrative examples of P,P-disubstituted phosphino groups include a dimethylphosphino group, a diethylphosphino group, a dipropylphosphino group, a diisopropyl phosphino group, a dicyclohexylphosphino group, a diphenylphosphino group, a bis(p-fluorophenyl)-phosphino group, a dibenzylphosphino group, a methylphenylphosphino group and an ethylphenylphosphino group. With respect to the non-coordinating anion represented by [J] - in formula II, any anion can be employed as long as the anion is stable under reaction conditions and is incapable of or hardly capable of forming a coordinate bond with transition metal M in formula II. Examples of such anions include halogenates, such as chlorate, bromate, iodate, perchlorate, perbromate and periodate; tetra-substituted borates, such as tetrafluoroborate, tetraphenylborate, tetrakis(p-fluorophenyl)borate, tetrakis(p-chlorophenyl)borate, tetrakis(pentafluorenyl)borate, tetratolylborate and tetrakis(2,4-dimethylphenyl)borate; polyborates, such as octadecaborate, tridecahydride-7-carbaundecaborate, bis(7,8-dicarbaundecaborate)cobaltate, bis(undecahydride-7,8-dicarbaundecaborate)nickelate and 1-carbadodecaborate; halide anions of Group VB of the Periodic Table, such as hexafluorophosphate and hexafluoroantim onate; tellurates, such as pentafluoroxotellurate; heteropoly anions, such as phosphotungstate and silicotungsate; a fullerene anion; and a methylenebistrifluorosulfonate. Of these, a tetra-substituted borate is especially preferred. Ligand L 1 is a trispyrazolyl tridentate ligand represented by the following formula III: In formula III, A is a carbon atom, or a boron atom substituted with a substituent selected from the group consisting of: a hydrogen atom; a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom; a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom; an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 -C 10 aromatic hydrocarbon group, or at least one halogen atom; a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 -C 10 aromatic hydrocarbon group, or at least one halogen atom; an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group. In formula III, each of Z 1 , Z 2 and Z 3 independently represents a pyrazolyl group represented by formula IV: wherein: each of R 3 , R 4 and R 5 independently represents: a hydrogen atom; a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom; a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom; an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group; a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 -C 10 aromatic hydrocarbon group, or at least one halogen atom; a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 -C 10 aromatic hydrocarbon group, or at least one halogen atom; an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group. In formula IV, a bridge bond is optionally formed between R 3 and R 4 or between R 3 and R 5 . Examples of such trispyrazolyl tridentate ligands include a hydrotrispyrazolylborate group; and derivatives thereof obtained by substituting the hydro group of the hydrotrispyrazolylborate group with alkyl, aryl or a heterocyclic ring, such as isopropyltrispyrazolylborate, n-butyltrispyrazolylborate, and tetrakispyrazolylborate (Class 1 ligands); Class 1 ligands having monosubstituted pyrazolyl, such as hydrotris(3-isopropylpyrazolyl)borate, hydrotris(3-t-butylpyrazolyl)borate, hydrotris(3-phenylpyrazolyl)borate, and hydrotris(3-(2'-thienyl)pyrazolyl)borate (Class 2 ligands); substitution isomers of Class 2 ligands, such as hydrobis(3-isopropylpyrazolyl)(5-isopropylpyrazolyl)borate and the like (Class 3 ligands); Class 1 ligands having disubstituted pyrazolyl, such as hydrotris(3,5-dimethylpyrazolyl)borate, isopropyltris(3,5-dimethylpyrazolyl)borate, n-butyltris(3,5-dimethylpyarzolyl)borate, tetrakis(3,5-dimethylpyarzolyl)borate, hydrotris(3,5-diisopropylpyrazolyl)borate, isopropyltris(3,5-diisopropylpyrazolyl)borate, n-butyltris(3,5-diisopropylpyrazolyl)borate, tetrakis(3,5-diisopropylpyrazolyl)borate, hydrotris(3,5-diphenylpyrazolyl)borate, isopropyltris(3,5-diphenylpyrazolyl)borate, n-butyl-tris(3,5-diphenylpyrazolyl)borate, tetrakis(3,5-diphenylpyrazolyl)borate and hydrotris(3-isopropyl-4-bromopyrazolyl)borate (Class 4 ligands); and substitution isomers of Class 4 ligands, such as hydrobis(3-isopropyl-4-bromopyrazolyl)(5-isopropyl-4-bromopyrazolyl)borate; ring-substituted Class 1 ligands, such as hydrotris(7-isopropyl-4-methyl-4,5,6,7-tetrahydro-2-indazoyl)borate (Class 5 ligands). Ligand L 2 is an alkapolyenyl ligand having a σ-bond and two or more π-bonds. As examples of such alkapolyenyl ligands, there can be mentioned alkatrienyl, cycloalkatrienyl, cycloalkadienyl and alkadienyl. An especially preferred example of an alkapolyenyl ligand is a ligand having a monocyclic or polycyclic alkadienyl skeleton represented by the following formula XI: C 5 H 5 - X R X wherein: H represents a hydrogen atom; X represents an integer of from 0 to 5; and each R independently represents: a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 - C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 , more preferably C 6 - C 14 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 -C 10 aromatic hydrocarbon group, or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 - C 20 , more preferably C 1 - C 10 , still more preferably C 1 - C 6 aliphatic hydrocarbon group, at least one C 6 - C 20 , more preferably C 6 - C 14 , still more preferably C 6 -C 10 aromatic hydrocarbon group, or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, or a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group. Examples of ligands represented by formula XI include a cyclopentadienyl group, a methylcyclopentadienyl group, an ethylcyclopentadienyl group, an n-propylcyclopentadienyl group, an isopropylcyclopentadienyl group, an n-butylcyclopentadienyl group, a trimethylsilylcyclopentadienyl group, a trimethylgermyl-cyclopentadienyl group, a 1,2-dimethylcyclopentadienyl group and 1,3- or 1,4-substitution isomers thereof, a 1,2,3-trimethylcyclopentadienyl group and substitution isomers thereof, a 1,2,3,4-tetramethylcyclopentadienyl group and substitution isomers thereof, a tetramethylcyclopentadienyl group, an unsubstituted or substituted indenyl group, an unsubstituted or substituted terahydroindenyl group, an unsubstituted or substituted fluorenyl group, and an unsubstituted or substituted octahydrofluorenyl group. The above-mentioned ligands may be bridge-bonded to ligand L 1 represented by formula III. When a bridge bond is formed between L 1 and L 2 , L 1 and L 2 may be bridge-bonded through a divalent group. Examples of such divalent groups through which L 1 and L 2 may be bridge bonded include an alkylene group, such as a methylene group, a diphenylmethylene group, an ethylene group, a propylene group and a cyclohexylene group; a silylene group, and derivatives thereof, such as a dimethylsilylene group and a diphenylsilylene group; a germylene group, and derivatives thereof, such as a dimethylgermylene group and a diphenylgermylene group; and a stannylene group, and derivatives thereof, such as a dimethylstannylene group and a diphenylstannylene group. In the present invention, a bridge bond may be formed within either of ligand L 1 and L 2 through a divalent hydrocarbon group, such as a methylene group, a diphenylmethylene group, an ethylene group, a propylene group, a butenylene group and a cyclohexylene group. The transition metal used in the catalyst of the present invention is selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII, more preferably metals of Groups IIIA, IVA, VA of the Periodic Table of the Elements. It is still more preferred that the transition metal used in the catalyst of the present invention is selected from metals of Groups IVA, such as titanium, zirconium and hafnium. The transition metal compound of the catalyst of the present invention is selected from compounds represented by the following formulae XII, XIII, XIV and XV: and wherein: M is a transition metal of Groups IVA of the Periodic Table of the Elements, X is an anionic ligand, J is a non-coordinating anion, L 1 and L 2 are ligands described above, and wherein a bridge bond may be formed between ligand L 1 and ligand L 2 . Examples of compounds of formula XII wherein M represents zirconium include those which can be classified into Class 1'. Class 1' (compounds having a combination of ligand L 1 and ligand L 2 , wherein L 1 is a trispyrazolyl tridentate ligand represented by formula III and ligand L 2 is an alkapolyenyl ligand having a σ-bond and two or more π-bonds): hydrotrispyrazolylboratocyclopentadienylzirconium dichloride, hydrotrispyrazolylboratocyclopentadienylzirconium dimethyl, hydrotrispyrazolylboratocyclopentadienylzirconium dibenzyl, hydrotrispyrazolylboratocyclopentadienylzirconium dimethoxide, hydrotrispyrazolylboratobutylcyclopentadienylzirconium dichloride, hydrotrispyrazolylboratobutylcyclopentadienylzirconium dimethyl, hydrotrispyrazolylboratobutylcyclopentadienylzirconium dibenzyl, hydrotrispyrazolylboratobutylcyclopentadienylzirconium dimethoxide, hydrotrispyrazolylboratopentamethylcyclopentadienylzirconium dichloride, hydrotrispyrazolylboratopentamethylcyclopentadienylzirconium dimethyl, hydrotrispyrazolylboratopentamethylcyclopentadienylzirconium dibenzyl, hydrotrispyrazolylboratopentamethylcyclopentadienylzirconium dimethoxide, hydrotrispyrazolylboratoindenylzirconium dicholoride, hydrotrispyrazolylboratoindenylzirconium dimethyl, hydrotrispyrazolylboratoindenylzirconium dibenzyl, hydrotrispyrazolylboratoindenylzirconium dimethoxide, hydrotrispyrazolylboratotetrahydroindenylzirconium dicholoride, hydrotrispyrazolylboratotetrahydroindenylzirconium dimethyl, hydrotrispyrazolylboratotetrahydroindenylzirconium dibenzyl, hydrotrispyrazolylboratotetrahydroindenylzirconium dimethoxide, hydrotrispyrazolylboratofluorenylzirconium dichloride, hydrotrispyrazolylboratofluorenylzirconium dimethyl, hydrotrispyrazolylboratofluorenylzirconium dibenzyl, hydrotrispyrazolylboratofluorenylzirconium dimethoxide, isopropyltrispyrazolylboratocyclopentadienylzirconium dichloride, isopropyltrispyrazolylboratocyclopentadienylzirconium dimethyl, isopropyltrispyrazolylboratocyclopentadienylzirconium dibenzyl, isopropyltrispyrazolylboratocyclopentadienylzirconium dimethoxide, isopropyltrispyrazolylboratobutylcyclopentadienylzirconium dichloride, isopropyltrispyrazolylboratobutylcyclopentadienylzirconium dimethyl, isopropyltrispyrazolylboratobutylcyclopentadienylzirconium dibenzyl, isopropyltrispyrazolylboratobutylcyclopentadienylzirconium dimethoxide, isopropyltrispyrazolylboratopentamethylcyclopentadienylzirconium dichloride, isopropyltrispyrazolylboratopentamethylcyclopentadie-nylzirconium dimethyl, isopropyltrispyrazolylboratopentamethylcyclopentadienylzirconium dibenzyl, isopropyltrispyrazolylboratopentamethylcyclopentadienylzirconium dimethoxide, isopropyltrispyrazolylboratoindenylzirconium dicholoride, isopropyltrispyrazolylboratoindenylzirconium dimethyl, isopropyltrispyrazolylboratoindenylzirconium dibenzyl, isopropyltrispyrazolylboratoindenylzirconium dimethoxide, isopropyltrispyrazolylboratotetraisopropylindenylzirconium dicholoride, isopropyltrispyrazolylboratotetraisopropylindenylzirconium dimethyl, isopropyltrispyrazolylboratotetraisopropylindenylzirconium dibenzyl, isopropyltrispyrazolylboratotetraisopropylindenylzirconium dimethoxide, isopropyltrispyrazolylboratofluorenylzirconium dichloride, isopropyltrispyrazolylboratofluorenylzirconium dimethyl, isopropyltrispyrazolylboratofluorenylzirconium dibenzyl, isopropyltrispyrazolylboratofluorenylzirconium dimethoxide, n-butyltrispyrazolylboratocyclopentadienylzirconium dichloride, n-butyltrispyrazolylboratocyclopentadienylzirconium dimethyl, n-butyltrispyrazolylboratocyclopentadienylzirconium dibenzyl, n-butyltrispyrazolylboratocyclopentadienylzirconium dimethoxide, n-butyltrispyrazolylboratobutylcyclopentadienylzirconium dichloride, n-butyltrispyrazolylboratobutylcyclopentadienylzirconium dimethyl, n-butyltrispyrazolylboratobutylcyclopentadienylzirconium dibenzyl, n-butyltrispyrazolylboratobutylcyclopentadienylzirconium dimethoxide, n-butyltrispyrazolylboratopentamethylcyclopentadienylzirconium dichloride, n-butyltrispyrazolylboratopentamethylcyclopentadienylzirconium dimethyl, n-butyltrispyrazolylboratopentamethylcyclopentadienylzirconium dibenzyl, n-butyltrispyrazolylboratopentamethylcyclopentadienylzirconium dimethoxide, n-butyltrispyrazolylboratoindenylzirconium dicholoride, n-butyltrispyrazolylboratoindenylzirconium dimethyl, n-butyltrispyrazolylboratoindenylzirconium dibenzyl, n-butyltrispyrazolylboratoindenylzirconium dimethoxide, n-butyltrispyrazolylboratotetra(n-butyl)indenylzirconium dicholoride, n-butyltrispyrazolylboratotetra(n-butyl)indenylzirconium dimethyl, n-butyltrispyrazolylboratotetra(n-butyl)indenylzirconium dibenzyl, n-butyltrispyrazolylboratotetra(n-butyl)indenylzirconium dimethoxide, n-butyltrispyrazolylboratofluorenylzirconium dichloride, n-butyltrispyrazolylboratofluorenylzirconium dimethyl, n-butyltrispyrazolylboratofluorenylzirconium dibenzyl, n-butyltrispyrazolylboratofluorenylzirconium dimethoxide, tetrakispyrazolylboratocyclopentadienylzirconium dichloride, tetrakispyrazolylboratocyclopentadienylzirconium dimethyl, tetrakispyrazolylboratocyclopentadienylzirconium dibenzyl, tetrakispyrazolylboratocyclopentadienylzirconium dimethoxide, tetrakispyrazolylboratobutylcyclopentadienylzirconium dichloride, tetrakispyrazolylboratobutylcyclopentadienylzirconium dimethyl, tetrakispyrazolylboratobutylcyclopentadienylzirconium dibenzyl, tetrakispyrazolylboratobutylcyclopentadienylzirconium dimethoxide, tetrakispyrazolylboratopentamethylcyclopentadienylzirconium dichloride, tetrakispyrazolylboratopentamethylcyclopentadienylzirconium dimethyl, tetrakispyrazolylboratopentamethylcyclopentadienylzirconium dibenzyl, tetrakispyrazolylboratopentamethylcyclopentadienylzirconium dimethoxide, tetrakispyrazolylboratoindenylzirconium dicholoride, tetrakispyrazolylboratoindenylzirconium dimethyl, tetrakispyrazolylboratoindenylzirconium dibenzyl, tetrakispyrazolylboratoindenylzirconium dimethoxide, tetrakispyrazolylboratotetrahydroindenylzirconium dicholoride, tetrakispyrazolylboratotetrahydroindenylzirconium dimethyl, tetrakispyrazolylboratotetrahydroindenylzirconium dibenzyl, tetrakispyrazolylboratotetrahydroindenylzirconium dimethoxide, tetrakispyrazolylboratofluorenylzirconium dichloride, tetrakispyrazolylboratofluorenylzirconium dimethyl, tetrakispyrazolylboratofluorenylzirconium dibenzyl, tetrakispyrazolylboratofluorenylzirconium dimethoxide, hydrotris(3-methylpyrazolyl)boratocyclopentadienylzirconium dichloride, hydrotris(3-methylpyrazolyl)boratocyclopentadienylzirconium dimethyl, hydrotris(3-methylpyrazolyl)boratocyclopentadienylzirconium dibenzyl, hydrotris(3-methylpyrazolyl)boratocyclopentadienylzirconium dimethoxide, hydrotris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dichloride, hydrotris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dimethyl, hydrotris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dibenzyl, hydrotris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dimethoxide, hydrotris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dichloride, hydrotris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethyl, hydrotris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dibenzyl, hydrotris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethoxide, hydrotris(3-methylpyrazolyl)boratoindenylzirconium dicholoride, hydrotris(3-methylpyrazolyl)boratoindenylzirconium dimethyl, hydrotris(3-methylpyrazolyl)boratoindenylzirconium dibenzyl, hydrotris(3-methylpyrazolyl)boratoindenylzirconium dimethoxide, hydrotris(3-methylpyrazolyl)boratotetrahydroindenylzirconium dicholoride, hydrotris(3-methylpyrazolyl)boratotetrahydroindenylzirconium dimethyl, hydrotris(3-methylpyrazolyl)boratotetrahydroindenylzirconium dibenzyl, hydrotris(3-methylpyrazolyl)boratotetrahydroindenylzirconium dimethoxide, hydrotris(3-methylpyrazolyl)boratofluorenylzirconium dichloride, hydrotris(3-methylpyrazolyl)boratofluorenylzirconium dimethyl, hydrotris(3-methylpyrazolyl)boratofluorenylzirconium dibenzyl, hydrotris(3-methylpyrazolyl)boratofluorenylzirconium dimethoxide, isopropyltris(3-methylpyrazolyl)boratocyclopentadienylzirconium dichloride, isopropyltris(3-methylpyrazolyl)boratocyclopentadienylzirconium dimethyl, isopropyltris(3-methylpyrazolyl)boratocyclopentadienylzirconium dibenzyl, isopropyltris(3-methylpyrazolyl)boratocyclopentadienylzirconium dimethoxide, isopropyltris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dichloride, isopropyltris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dimethyl, isopropyltris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dibenzyl, isopropyltris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dimethoxide, isopropyltris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dichloride, isopropyltris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethyl, isopropyltris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dibenzyl, isopropyltris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethoxide, isopropyltris(3-methylpyrazolyl)boratoindenylzirconium dicholoride, isopropyltris(3-methylpyrazolyl)boratoindenylzirconium dimethyl, isopropyltris(3-methylpyrazolyl)boratoindenylzirconium dibenzyl, isopropyltris(3-methylpyrazolyl)boratoindenylzirconium dimethoxide, isopropyltris(3-methylpyrazolyl)boratotetraisopropylindenylzirconium dicholoride, isopropyltris(3-methylpyrazolyl)boratotetraisopropylindenylzirconium dimethyl, isopropyltris(3-methylpyrazolyl)boratotetraisopropylindenylzirconium dibenzyl, isopropyltris(3-methylpyrazolyl)boratotetraisopropylindenylzirconium dimethoxide, isopropyltris(3-methylpyrazolyl)boratofluorenylzirconium dichloride, isopropyltris(3-methylpyrazolyl)boratofluorenylzirconium dimethyl, isopropyltris(3-methylpyrazolyl)boratofluorenylzirconium dibenzyl, isopropyltris(3-methylpyrazolyl)boratofluorenylzirconium dimethoxide, n-butyltris(3-methylpyrazolyl)boratocyclopentadienylzirconium dichloride, n-butyltris(3-methylpyrazolyl)boratocyclopentadienylzirconium dimethyl, n-butyltris(3-methylpyrazolyl)boratocyclopentadienylzirconium dibenzyl, n-butyltris(3-methylpyrazolyl)boratocyclopentadienylzirconium dimethoxide, n-butyltris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dichloride, n-butyltris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dimethyl, n-butyltris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dibenzyl, n-butyltris(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dimethoxide, n-butyltris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dichloride, n-butyltris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethyl, n-butyltris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dibenzyl, n-butyltris(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethoxide, n-butyltris(3-methylpyrazolyl)boratoindenylzirconium dicholoride, n-butyltris(3-methylpyrazolyl)boratoindenylzirconium dimethyl, n-butyltris(3-methylpyrazolyl)boratoindenylzirconium dibenzyl, n-butyltris(3-methylpyrazolyl)boratoindenylzirconium dimethoxide, n-butyltris(3-methylpyrazolyl)boratotetra(n-butyl)indenylzirconium dicholoride, n-butyltris(3-methylpyrazolyl)boratotetra(n-butyl)indenylzirconium dimethyl, n-butyltris(3-methylpyrazolyl)boratotetra(n-butyl)indenylzirconium dibenzyl, n-butyltris(3-methylpyrazolyl)boratotetra(n-butyl)indenylzirconium dimethoxide, n-butyltris(3-methylpyrazolyl)boratofluorenylzirconium dichloride, n-butyltris(3-methylpyrazolyl)boratofluorenylzirconium dimethyl, n-butyltris(3-methylpyrazolyl)boratofluorenylzirconium dibenzyl, n-butyltris(3-methylpyrazolyl)boratofluorenylzirconium dimethoxide, tetrakis(3-methylpyrazolyl)boratocyclopentadienylzirconium dichloride, tetrakis(3-methylpyrazolyl)boratocyclopentadienylzirconium dimethyl, tetrakis(3-methylpyrazolyl)boratocyclopentadienylzirconium dibenzyl, tetrakis(3-methylpyrazolyl)boratocyclopentadienylzirconium dimethoxide, tetrakis(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dichloride, tetrakis(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dimethyl, tetrakis(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dibenzyl, tetrakis(3-methylpyrazolyl)boratobutylcyclopentadienylzirconium dimethoxide, tetrakis(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dichloride, tetrakis(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethyl, tetrakis(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dibenzyl, tetrakis(3-methylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethoxide, tetrakis(3-methylpyrazolyl)boratoindenylzirconium dicholoride, tetrakis(3-methylpyrazolyl)boratoindenylzirconium dimethyl, tetrakis(3-methylpyrazolyl)boratoindenylzirconium dibenzyl, tetrakis(3-methylpyrazolyl)boratoindenylzirconium dimethoxide, tetrakis(3-methylpyrazolyl)boratotetrahydroindenylzirconium dicholoride, tetrakis(3-methylpyrazolyl)boratotetrahydroindenylzirconium dimethyl, tetrakis(3-methylpyrazolyl)boratotetrahydroindenylzirconium dibenzyl, tetrakis(3-methylpyrazolyl)boratotetrahydroindenylzirconium dimethoxide, tetrakis(3-methylpyrazolyl)boratofluorenylzirconium dichloride, tetrakis(3-methylpyrazolyl)boratofluorenylzirconium dimethyl, tetrakis(3-methylpyrazolyl)boratofluorenylzirconium dibenzyl, tetrakis(3-methylpyrazolyl)boratofluorenylzirconium dimethoxide, hydrotris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dichloride, hydrotris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dimethyl, hydrotris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dibenzyl, hydrotris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dimethoxide, hydrotris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dichloride, hydrotris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dimethyl, hydrotris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dibenzyl, hydrotris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dimethoxide, hydrotris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dichloride, hydrotris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethyl, hydrotris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dibenzyl, hydrotris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethoxide, hydrotris(3,5-dimethylpyrazolyl)boratoindenylzirconium dicholoride, hydrotris(3,5-dimethylpyrazolyl)boratoindenylzirconium dimethyl, hydrotris(3,5-dimethylpyrazolyl)boratoindenylzirconium dibenzyl, hydrotris(3,5-dimethylpyrazolyl)boratoindenylzirconium dimethoxide, hydrotris(3,5-dimethylpyrazolyl)boratotetrahydroindenylzirconium dicholoride, hydrotris(3,5-dimethylpyrazolyl)boratotetrahydroindenylzirconium dimethyl, hydrotris(3,5-dimethylpyrazolyl)boratotetrahydroindenylzirconium dibenzyl, hydrotris(3,5-dimethylpyrazolyl)boratotetrahydroindenylzirconium dimethoxide, hydrotris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dichloride, hydrotris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dimethyl, hydrotris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dibenzyl, hydrotris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dimethoxide, isopropyltris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dichloride, isopropyltris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dimethyl, isopropyltris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dibenzyl, isopropyltris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dimethoxide, isopropyltris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dichloride, isopropyltris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dimethyl, isopropyltris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dibenzyl, isopropyltris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dimethoxide, isopropyltris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dichloride, isopropyltris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethyl, isopropyltris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dibenzyl, isopropyltris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethoxide, isopropyltris(3,5-dimethylpyrazolyl)boratoindenylzirconium dicholoride, isopropyltris(3,5-dimethylpyrazolyl)boratoindenylzirconium dimethyl, isopropyltris(3,5-dimethylpyrazolyl)boratoindenylzirconium dibenzyl, isopropyltris(3,5-dimethylpyrazolyl)boratoindenylzirconium dimethoxide, isopropyltris(3,5-dimethylpyrazolyl)boratotetraisopropylindenylzirconium dicholoride, isopropyltris(3,5-dimethylpyrazolyl)boratotetraisopropylindenylzirconium dimethyl, isopropyltris(3,5-dimethylpyrazolyl)boratotetraisopropylindenylzirconium dibenzyl, isopropyltris(3,5-dimethylpyrazolyl)boratotetraisopropylindenylzirconium dimethoxide, isopropyltris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dichloride, isopropyltris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dimethyl, isopropyltris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dibenzyl, isopropyltris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dimethoxide, n-butyltris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dichloride, n-butyltris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dimethyl, n-butyltris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dibenzyl, n-butyltris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dimethoxide, n-butyltris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dichloride, n-butyltris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dimethyl, n-butyltris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dibenzyl, n-butyltris(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dimethoxide, n-butyltris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dichloride, n-butyltris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethyl, n-butyltris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dibenzyl, n-butyltris(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethoxide, n-butyltris(3,5-dimethylpyrazolyl)boratoindenylzirconium dicholoride, n-butyltris(3,5-dimethylpyrazolyl)boratoindenylzirconium dimethyl, n-butyltris(3,5-dimethylpyrazolyl)boratoindenylzirconium dibenzyl, n-butyltris(3,5-dimethylpyrazolyl)boratoindenylzirconium dimethoxide, n-butyltris(3,5-dimethylpyrazolyl)boratotetra(n-butyl)indenylzirconium dicholoride, n-butyltris(3,5-dimethylpyrazolyl)boratotetra(n-butyl)indenylzirconium dimethyl, n-butyltris(3,5-dimethylpyrazolyl)boratotetra(n-butyl)indenylzirconium dibenzyl, n-butyltris(3,5-dimethylpyrazolyl)boratotetra(n-butyl)indenylzirconium dimethoxide, n-butyltris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dichloride, n-butyltris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dimethyl, n-butyltris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dibenzyl, n-butyltris(3,5-dimethylpyrazolyl)boratofluorenylzirconium dimethoxide, tetrakis(3,5-dimethylpyrazolyl)boratocyclopentadienyl-zirconium dichloride, tetrakis(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dimethyl, tetrakis(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dibenzyl, tetrakis(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dimethoxide, tetrakis(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dichloride, tetrakis(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dimethyl, tetrakis(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dibenzyl, tetrakis(3,5-dimethylpyrazolyl)boratobutylcyclopentadienylzirconium dimethoxide, tetrakis(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dichloride, tetrakis(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethyl, tetrakis(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dibenzyl, tetrakis(3,5-dimethylpyrazolyl)boratopentamethylcyclopentadienylzirconium dimethoxide, tetrakis(3,5-dimethylpyrazolyl)boratoindenylzirconium dicholoride, tetrakis(3,5-dimethylpyrazolyl)boratoindenylzirconium dimethyl, tetrakis(3,5-dimethylpyrazolyl)boratoindenylzirconium dibenzyl, tetrakis(3,5-dimethylpyrazolyl)boratoindenylzirconium dimethoxide, tetrakis(3,5-dimethylpyrazolyl)boratotetrahydroindenylzirconium dicholoride, tetrakis(3,5-dimethylpyrazolyl)boratotetrahydroindenylzirconium dimethyl, tetrakis(3,5-dimethylpyrazolyl)boratotetrahydroindenylzirconium dibenzyl, tetrakis(3,5-dimethylpyrazolyl)boratotetrahydroindenylzirconium dimethoxide, tetrakis(3,5-dimethylpyrazolyl)boratofluorenylzirconium dichloride, tetrakis(3,5-dimethylpyrazolyl)boratofluorenylzirconium dimethyl, tetrakis(3,5-dimethylpyrazolyl)boratofluorenylzirconium dibenzyl, tetrakis(3,5-dimethylpyrazolyl)boratofluorenylzirconium dimethoxide, substituted compounds of the above-mentioned compounds, and compounds having the same nomenclatures as those of the above compounds except that "substituted borato" is replaced with a term "methanido". In place of the zirconium atom as a central metal of the above-mentioned zirconium compounds, other metals, such as titanium and hafnium, can be used. Further, in place of the anionic ligands used in the above-mentioned compounds, other types of non-coordinating anions can be used, so that a structure of the resultant compound is represented by formula XIII. Examples of compounds of formula XIV wherein M represents zirconium include those which can be classified into Class 2'. Class 2' (compounds having a combination of ligand L 1 and ligand L 2 , wherein L 1 is a trispyrazolyl tridentate ligand represented by formula III and ligand L 2 is an alkapolyenyl ligand having a σ-bond and two or more π-bonds, wherein a bridge bond is formed between ligand L 1 and ligand L 2 ): hydrobis(3,5-dimethylpyrazolyl)(3-(ethylenecyclopentadienyl)pyrazolyl)boratozirconium dichloride, hydrobispyrazolyl(3-(ethylenecyclopentadienyl)pyrazolyl)boratozirconium dimethyl, hydrobispyrazolyl(3-(dimethylsilylenecyclopentadienyl)pyrazolyl)boratozirconium dichloride, hydrobispyrazolyl(3-(dimethylsilylenecyclopentadienyl)pyrazolyl)boratozirconium dimethyl, hydrobispyrazolyl(3-(ethyleneindenyl)pyrazolyl)boratozirconium dichloride, hydrobispyrazolyl(3-(ethyleneindenyl)pyrazolyl)boratozirconium dimethyl, hydrobispyrazolyl(3-(dimethylsilyleneindenyl)pyrazolyl)boratozirconium dichloride, hydrobispyrazolyl(3-(dimethylsilyleneindenyl)pyrazolyl)boratozirconium dimethyl, hydrobispyrazolyl(3-(ethylenetetrahydroindenyl)pyrazolyl)boratozirconium dichloride, hydrobispyrazolyl(3-(ethylenetetrahydroindenyl)pyrazolyl)boratozirconium dimethyl, hydrobispyrazolyl(3-(dimethylsilylenetetrahydroindenyl)pyrazolyl)boratozirconium dichloride, and hydrobispyrazolyl(3-(dimethylsilylenetetrahydroindenyl)pyrazolyl)boratozirconium dimethyl. In place of the zirconium atom as a central metal of the above-mentioned zirconium compounds, other metals, such as titanium and hafnium, can be used. Further, in place of the anionic ligands used in the above-mentioned compounds, other types of non-coordinating anions can be used, so that a structure of the resultant compound is represented by formula XV. The catalyst of the present invention may be used alone for olefin polymerization. However, the catalyst of the present invention may be used together with an auxiliary catalyst comprised of alkylaluminoxane which is represented by one of the following formulae XVI and XVII: and wherein each R independently represents a hydrogen atom, a halogen atom or a C 1 - C 10 alkyl group, and n is an integer of from 1 to 40. Representative examples of Rs in formulae (XVI) and (XVII) include a hydrogen atom, a chlorine atom, a bromine atom, a methyl group, an ethyl group, an n-propyl group, an isoprolyl group, an n-butyl group, an isobutyl group, an s-butyl group, a propyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a nonyl group and a decyl group. It is preferred that at least one R represent a methyl group. The number of recurring units (i.e., n) is preferably in the range from 2 to 40, more preferably 5 to 40. The alkylaluminoxane can be prepared by a customary method. For example, in one customary method, trialkylaluminum is dissolved in a hydrocarbon solvent to obtain a solution and then, an equivalent amount of water, relative to the amount of the trialkylaluminum, is gradually added to the solution to hydrolyze the trialkylaluminum. In another customary method, copper sulfate hydrate or aluminum sulfate hydrate is suspended in a hydrocarbon solvent and then, trialkylaluminum (in an amount 1 to 3 equivalents relative to one equivalent of the crystal water of the suspended hydrate) is contacted with the hydrate to thereby gradually hydrolyze the trialkylaluminum. In still another customary method, silica gel having water adsorbed thereon is suspended in a hydrocarbon solvent and then, trialkylaluminum (in an amount 1 to 3 equivalents relative to one equivalent of the water adsorbed on the suspended silica gel) is contacted with the silica gel to thereby gradually hydrolyze the trialkylaluminum. Another example of an auxiliary catalyst which may be used together with the catalyst of the present invention is a cation producer represented by the following formula XVIII: [ On ] + [ An ] - wherein: [On] + represents a metal cation, such as a cation of a metal of Group IB, Group IIB or Group VIII of the Periodic Table of the Elements, or an onium, such as carbonium, silonium, oxonium, sulfonium, ammonium or phosphonium; and [An] - represents an anion which is stable under the reaction conditions for olefin polymerization and has no or poor coordinating properties. Preferred examples of cation producers represented by formula (XVIII) include tetra (pentafluorophenyl) borates, such as ferroceniumtetra(pentafluorophenyl) borate, silver (I) tetra(pentafluorophenyl)borate, copper (I) tetra(pentafluorophenyl)borate, mercury (II) bis(tetra(pentafluorophenyl)borate), palladium (II) bis(tetra(pentafluorophenyl)borate), platinum (II) bis(tetra(pentafluorophenyl)borate), diphenylhydrocarboniumtetra(pentafluorophenyl)borate, triphenylcarboniumtetra(pentafluorophenyl)borate, triphenylsiloniumtetra(pentafluorophenyl)borate, tricyclohexylcarboniumtetra(pentafluorophenyl)borate, triethyloxoniumtetra(pentafluorophenyl)borate, triethylsulfoniumtetra(pentafluorophenyl)borate, diethylaniliniumtetra(pentafluorophenyl)borate, trimethylammoniumtetra(pentafluorophenyl)borate, triethylammoniumtetra(pentafluorophenyl)borate, tetra(n-butyl) ammoniumtetra(pentafluorophenyl)borate and triphenylphosphoniumtetra(pentafluorophenyl)borate. A further example of an auxiliary catalyst is an alkylaluminum represented by the following formula XIX: ( R 3 Al ) n wherein each R independently represents a hydrogen atom, a halogen atom and a C 1 - C 10 alkyl group, and n is 1 or 2. This auxiliary catalyst is effective for stabilizing the catalyst of the present invention and for stabilizing an alkylaluminoxane used as an auxiliary catalyst so that the amount of alkylaluminoxane to be used can be reduced. Examples of Rs include a hydrogen atom, a chlorine atom, a bromine atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a propyl group, a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group. It is preferred that at least one R represent a methyl group. In conducting olefin polymerization using the catalyst of the present invention, it is preferred that the catalyst of the present invention be used in an amount such that the concentration of the transition metal of the catalyst is in the range from 10 -10 to 10 -1 mol/liter of the liquid medium, more preferably from 10 -8 to 10 -3 mol/liter of the liquid medium. (When an olefin is polymerized in the gaseous phase, the "liquid medium" means a solvent to be used while when an olefin is polymerized is in the liquid phase, the "liquid medium" means the liquid olefin or a mixture of a solvent to be used and the liquid olefin). When olefin polymerization is conducted by a gas phase polymerization method, the catalyst is used in a form carried on a carrier. In this case, it is preferred that the amount of the transition metal of the catalyst be 10 -7 to 10 -2 gram atom/g of the carrier, more preferably 10 -5 to 10 -3 gram atom/g of the carrier. When alkylaluminoxane is used as an auxiliary catalyst, it is preferred that alkylaluminoxane be used in an amount such that the atomic ratio of the aluminum contained in the alkylaluminoxane to the transition metal contained in the catalyst is in the range from 1 to 10 6 , more preferably from 1 to 10 4 . When the above-mentioned cation producer is employed as an auxiliary catalyst, it is prefered that the cation producer be used in an amount such that the atomic ratio of the cation in the cation producer to the transition metal contained in the catalyst is in the range from 0.1 to 10, preferably from 0.5 to 2. In order to increase a bulk density of a polymer to be produced, improve the powder characteristics of the polymer, and control a molecular weight distribution of the polymer, the catalyst of the present invention can be used in a state carried on a carrier. Examples of materials for carriers include an organic material, such as starch or a polymer, a metallic material, such as bismuth, powdery copper or powdery iron, a metal oxide, such as alumina or iron oxide, a metal carbonate, such as magnesium carbonate, a metal chloride, such as magnesium chloride, activated carbon, an inorganic carbide, such as silicon carbide, an inorganic silicon oxide, such as silica, zeolite or diatomite and an ion-exchange resin, such as Amberlite or Nafion. Generally, these carrier materials contain an active hydrogen-containing compound, such as crystal water, adsorbed water or a hydroxyl group, which can react with the catalyst to deactivate the same. Therefore, it is preferred that before introduction into the reaction system, these carrier materials be subjected to appropriate treatment for removing the active hydrogen. For example, in such a treatment, active hydrogen atoms, which are contained in the hydroxy groups of an organic material, in the silanol groups of an inorganic silicon oxide or in the amino groups or hydroxyl groups of an ion-exchange resin, can be removed by contacting carriers containing the active hydrogen atoms with alkylaluminum or alkylaluminoxane (which is used in an amount 0.3 to 5 equivalents (in terms of aluminum atoms) relative to one equivalent of the active hydrogen atom. With respect to carrier materials composed of a metal, a metal oxide, a metal carbonate, a metal chloride, an inorganic carbonate, and inorganic silicon oxide, the crystal water and adsorbed water of these carriers can be removed therefrom by sintering these carrier materials at an appropriate temperature. The treatment for removing the active hydrogen from a carrier can be conducted before or after a catalyst is carried on the carrier. At least one of the catalyst of the present invention, the alkylaluminoxane auxiliary catalyst, the cation producer as an auxiliary catalyst and the alkylaluminum auxiliary catalyst can be carried on a carrier in any combination and in any order. Hereinafter, explanation is made on the polymerization of an olefin using the catalyst of the present invention. The catalyst of the present invention can be advantageously used for polymerization of various olefins. Examples of olefins which can be polymerized using the catalyst of the present invention include an α-olefin, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene or vinylcyclohexane; a vinyl aromatic hydrocarbon, such as styrene or methylstyrene; an alicyclic olefin, such as cyclopentene, methylcyclopentene, cycloheptene, or cyclooctene; a conjugated diene, such as butadiene, 1,3-pentadiene, 1,3-hexadiene, cyclopentadiene, 1,3-cyclohexadiene or vinyl-1-cyclohexene; an unconjugated diene, such as 1,4-pentadiene, 1,5-hexadiene, 1,4-hexadiene, 2-methyl-1,4-pentadiene, 3-vinylcyclohexene or 4-vinyl-3-norbornene; a polyene having 6 to 20 carbon atoms; acetylene; propyne; butyne; pentyne; and hexyne. Of them, an α-olefin is preferred and ethylene is more preferred. The catalyst of the present invention can also be used for copolymerization between two or more different types of olefins. For example, there can be mentioned copolymerization between ethylene and one or more comonomers, e.g., an α-olefin, such as propylene, 1-butene or 1-hexene; a vinylaromatic hydrocarbon, such as styrene or methylstyrene; an alicyclic olefin, such as cyclopentene or methylcyclopentene; a conjugated diene, such as butadiene; an unconjugated diene, such as 1,5-hexadiene or 3-vinylcyclohexene; a polyene; and acetylene. In connection with the above, it is noted that the types of catalysts are not particularly limited with respect to the types of olefins to be polymerized. For the polymerization of an olefin, there may be employed a customary polymerization method, such as a suspension polymerization method, a solution polymerization method and a gas phase polymerization method. In a suspension polymerization method, for example, a catalyst is charged, together with a polymerization solvent, in a reaction vessel and then, thereto is added an olefin in an inert atmosphere under a pressure of 1 to 200 kg/cm 2 G (1 kg/cm 2 G = 0.981 bar G). A polymerization reaction is then allowed to proceed at a temperature of from -50 °C to 120 °C. Examples of solvents to be used in the polymerization reaction include aliphatic hydrocarbons, such as propane, butane, pentane, hexane, heptane, octane and nonane; alicyclic hydrocarbons, such as cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, cyclooctane and isopropylcyclohexane; aromatic hydrocarbons, such as benzene, toluene, xylene and t-butylbenzene; perfluoro aliphatic hydrocarbons, such as perfluorooctane and perfluorononane, and mixtures of these hydrocarbons. In a solution polymerization method, for example, a catalyst is introduced, together with a polymerization solvent, in a reaction vessel and then, thereto is added an olefin in an inert atmosphere under a pressure of from 1 to 200 kg/cm 2 G. A polymerization reaction is allowed to proceed at a temperature of from 50 °C to 300 °C. Examples of solvents to be used in the polymerization reaction include aliphatic hydrocarbons, such as propane, butane, pentane, hexane, heptane, octane and nonane; alicyclic hydrocarbons, such as cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, cyclooctane and isopropylcyclohexane; aromatic hydrocarbons, such as benzene, toluene, xylene and t-butylbenzene; perfluoro aliphatic hydrocarbons, such as perfluorooctane and perfluorononane, and mixtures of these hydrocarbons. In a gas phase polymerization method, for example, a catalyst is placed in a reaction vessel and an olefin is charged in the reaction vessel in an inert atmosphere under a pressure of from 1 to 50 kg/cm 2 G. A polymerization reaction is allowed to proceed at a temperature of from -50 °C to 120 °C. During the polymerization, frequency of contact between olefin molecules and the catalyst molecules can be increased by employng a mixing apparatus, such as a fluidized bed or a moving bed, or by stirring. The polymerization may be conducted by a mono-stage polymerization method in which a single reaction stage is employed, or by a multi-stage polymerization method in which a plurality of reaction stages are involved. In the case of the multi-stage polymerization method, when the polymerization reaction is conducted using two or more different sets of reaction conditions, a polymer having a broad molecular weight distribution can be produced. If desired for controlling a molecular weight of a polymer to be produced, customary techniques may be employed, such as controlling of the reaction temperature and an addition of hydrogen to the reaction system. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The present invention will now be described in greater detail with reference to the following Examples and Comparative Examples which should not be construed as limiting the scope of the present invention. In the Examples and Comparative Examples, a catalytic activity represents an yield (g) of a polymer formed per gram of a metal contained in a catalyst per hour. Further, MI represents a melt index which is measured at a temperature of 190 °C under a load of 2.16 kg, while HMI represents a melt index measured at 190 °C under a load of 21.6 kg. Both of MI and HMI are measured according to ASTM D-1238. A molecular weight and a molecular weight distribution of a polymer are obtained, from a differential refractive index and viscosity, by gel permeation chromatography (apparatus: 150 CV manufactured and sold by Waters Assoc. Co., U.S.A.). Mw represents a weight average molecular weight, and Mn represents a number average molecular weight. [Polymerization of ethylene] Example 1 Synthesis of catalyst C1 Hydrotrispyrazolylboratocyclopentadienylzirconium dichloride {HB(pz) 3 CpZrCl 2 }, wherein pz represents a pyrazolyl group, and Cp represents a cyclopentadienyl group, is synthesized according to the method described in "J. Chem. Soc. Dalton Trans.", page 603 (1991). Polymerization reaction A 3 ml toluene solution containing 1.0 µmole of catalyst C1 {HB(pz) 3 CpZrCl 2 } and 0.7 ml (2.0 mmoles in terms of the amount of aluminum) of a toluene solution of methylaluminoxane (PMAO; containing 2.92 moles of aluminum/liter of the toluene solution) (manufactured and sold by Tosoh Akzo Corp., Japan) are charged, together with 0.8 liter of dehydrated and deoxygenated toluene, in a 1.6-liter autoclave evacuated and replaced with nitrogen gas. The temperature of the inside of the autoclave is maintained at 80 °C and then, ethylene gas is charged in the autoclave at a pressure of 10 kg/cm 2 G. A total pressure of the autoclave becomes 10.4 kg/cm 2 G, including a solvent pressure. A polymerization reaction is allowed to proceed for 1 hour, while the total pressure of the autoclave is maintained constantly by supplying ethylene gas. 42 g of a polymer is obtained. It is found that a catalytic activity of catalyst C1 is 4,600 kg/g of Zr per hour, the molecular weight of the polymer is 1,290,000, the molecular weight distribution is 2.56 in terms of Mw/Mn and HMI is 0.29 g/10 min. Example 2 Synthesis of catalyst C2 Hydrotris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dichloride {HB(3,5-Me 2 pz) 3 CpZrCl 2 }, wherein 3,5-Me 2 pz represents a 3,5-dimethylpyrazolyl group, is synthesized according to the method described in "Inorganic chemistry", page 2046 (1986). Polymerization reaction A 3 ml toluene solution containing 0.1 µmole of catalyst C2 {HB(3,5-Me 2 pz) 3 CpZrCl 2 } and 0.035 ml (0.1 mmole in terms of the amount of aluminum) of a toluene solution of methylaluminoxane (PMAO; containing 2.92 moles of aluminum/liter of the toluene solution) (manufactured and sold by Tosoh Akzo Corp., Japan) are charged, together with 0.8 liter of dehydrated and deoxygenated toluene, in a 1.6-liter autoclave evacuated and replaced with nitrogen gas. The temperature of the inside of the autoclave is maintained at 80 °C and then, ethylene gas is charged in the autoclave at a pressure of 10 kg/cm 2 G. A total pressure of the autoclave becomes 10.4 kg/cm 2 G, including a solvent pressure. A polymerization reaction is allowed to proceed for 1 hour, while the total pressure of the autoclave is maintained constantly by supplying ethylene gas. 17.2 g of a polymer is obtained. It is found that a catalytic activity of catalyst C2 is 1,890 kg/g of Zr per hour, the molecular weight of the polymer is 1,230,000, the molecular weight distribution is 2.53 in terms of Mw/Mn and HMI is 0.23 g/10 min. Comparative Example 1 Synthesis of comparative catalyst a Pyrazolylcyclopentadienylzirconium dichloride {pzCpZrCl 2 } is synthesized as follows. To a 100 ml diethyl ether solution containing 0.011 mole of pyrazolyllithium salt is gradually added 0.01 mole of zirconium chloride, followed by stirring for one day. Subsequently, 100 ml of a diethyl ether solution of cyclopentadienelithium salt is added to the mixture and then, stirred for one day. Subsequently, the ether is evaporated under a vacuum and then, pentane is added thereto to precipitate lithium chloride. The precipitate is separated by filtration to obtain a filtrate. The obtained filtrate is filtered two times through sellaite to obtain a catalyst in a solid form. Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 3 ml toluene solution containing 1.0 µmole of comparative catalyst a {pzCpZrCl 2 } is used instead of catalyst C1. 0.6 g of a polymer is obtained. It is found that a catalytic activity of comparative catalyst a having a monodentate ligand containing a hetero atom is as low as 6.6 kg/g of Zr per hour. Comparative Example 2 Synthesis of comparative catalyst intermediate I1 Hydrotrispyrazolylboratozirconium trichloride {HB(pz) 3 ZrCl 3 } is synthesized according to the method described in "Inorganic Chemistry", page 1065 (1983). Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 3 ml toluene solution containing 1.0 µmole of comparative catalyst intermediate I1 {HB(pz) 3 ZrCl 3 } is used instead of catalyst C1. 2.6 g of a polymer is obtained. It is found that a catalytic activity of comparative catalyst intermediate I1 having only a trispyrazolyl ligand is as low as 29 kg/g of Zr per hour. Comparative Example 3 Synthesis of comparative catalyst intermediate I2 Hydrotris(3,5-dimethylpyrazolyl)boratozirconium trichloride {HB(3,5-Me 2 pz) 3 ZrCl 3 } is synthesized according to the method described in "Inorganic Chemistry", page 840(1982). Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 3 ml toluene solution containing 1.0 µmole of comparative catalyst intermediate I2 {HB(3,5-Me 2 pz) 3 ZrCl 3 } is used instead of catalyst C1. 1.8 g of polymer is obtained. It is found that a catalytic activity of comparative catalyst intermediate I2 having only a trispyrazolyl ligand is as low as 20.1 kg/g of Zr per hour. Example 3 Synthesis of catalyst C3 Hydrotris(3,5-dimethylpyrazolyl)boratoindenylzirconium dichloride {HB(3,5-Me 2 pz) 3 IndZrCl 2 , wherein Ind represents an indenyl group, is synthesized as follows. A 1-liter four-necked flask provided with a dropping funnel, a stirrer and a thermometer is replaced with nitrogen gas. To the flask are charged 10 mmoles of intermediate product I2 which has been synthesized in Comparative Example 3 and 10 mmoles of indenyllithium (for example, see "Experimental Chemistry", Vol. 18, 4th ed., edited by The Chemical Society of Japan, published by Maruzen Co., Ltd., Japan). The temperature inside the flask is lowered to -78 °C in a nitrogen atmosphere and then, toluene kept at -78 °C is added thereto through a dropping funnel to obtain a suspension. The obtained suspension is stirred for one day, while maintaining the temperature of the suspension under ice-cooled conditions. The reaction mixture is filtered through diatomaceous earth to obtain a filtrate. After the filtrate is concentrated 5-fold, hexane is added to the concentrate, so that a white solid is precipitated. The precipitate is separated by filtration and then, recrystallized to obtain a product. Identification of the product as {HB(3,5-Me 2 pz) 3 IndZrCl 2 is made by 1 H-NMR spectroscopy (heavy toluene, 270 MH) which shows signals for the ligand at 6 2.25 (S, 18H, Me group), 5.8 (S, 3H, 4-H of pyrazolyl group) and 7.1-7.9 (m, 7H, indenyl group). Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 3 ml toluene solution containing 2.0 µmoles of catalyst C3 {HB(3,5-Me 2 pz) 3 IndZrCl 2 } is used instead of catalyst C1. 35 g of polymer is obtained. It is found that a catalytic activity of C3 is 192 kg/g of Zr per hour. Example 4 Synthesis of catalyst C4 Hydrotris(3,5-dimethylpyrazolyl)borato(pentamethylcyclopentadienyl)zirconium dichloride {HB(3,5-Me 2 pz) 3 CpZrCl 2 }, wherein Cp represents a pentamethylcyclopentadienyl group, is synthesized according to the procedure as described in Example 2. Identification of C4 is made by 1 H-NMR spectroscopy (heavy toluene, 270 MH), which shows signals of the ligands at δ 2.25 (S, 18H, Me group), 2.45 (S, 15H, Cp group) and 5.8 (S, 3H, 4-H of pz group). Polymerization reaction Substantially the same polymerization procedure as described in Example 1 is repeated except that a 3 ml toluene solution containing 1.0 µmole of catalyst C4, (HB(3,5-Me 2 pz) 3 CpZrCl 2 is used instead of catalyst C1. 53 g of a polymer is obtained. The catalytic activity of catalyst C4 is 593 kg/g of Zr per hour. Example 5 Synthesis of catalyst C5 Hydrotris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dibenzyl {HB(3,5-Me 2 pz) 3 CpZr(CH 2 Ph) 2 } is synthesized as follows. A 1-liter four-necked flask provided with a reflux column which is connected at a top thereof to a gas buret for measuring an amount of a generated gas, a dropping funnel, a stirrer and a thermometer is purged with nitrogen gas. To the flask are charged 10 mmoles of catalyst C2 and 50 ml of diethyl ether cooled at -78 °C. Subsequently, thereto dropwise added is 30 ml of 1 M diethyl ether solution of magnesium benzylchloride, PhCH 2 MgCl over a period of 1 hour. A formed solid is filtered off to obtain a filtrate. The obtained filtrate is condensed to 10 ml and then, thereto added is dried pentane to cause crystallization. Polymerization reaction Substantially the same polymerization procedure as described in Example 2 is repeated except that a 3 ml toluene solution containing 0.1 µmole of catalyst C5, {HB(3,5-Me 2 pz) 3 CpZr(CH 2 Ph) 2 } is used instead of the catalyst C2. 19 g of a polymer is obtained. The catalytic activity of C5 is 2,080 kg/g of Zr per hour. Example 6 Synthesis of catalyst C6 Hydrotris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dimethoxide {HB(3,5-Me 2 pz) 3 CpZr(OMe) 2 } is synthesized as follows. In the same apparatus as used in Example 5 for synthesizing catalyst C5 are charged 10 mmoles of catalyst C2 and 50 ml of toluene cooled at -78 °C. Subsequently, thereto dropwise added is 30 ml of 1 M toluene solution of methoxylithium over a period of 1 hour to obtain a mixture. The obtained mixture is further stirred for 24 hours. A formed solid is filtered off to obtain a filtrate. The obtained filtrate is condensed to 10 ml and then, thereto added is dried hexane to cause crystallization. Polymerization reaction Substantially the same polymerization procedure as described in Example 2 is repeated except that a 3 ml toluene solution containing 0.1 µmole of catalyst C6, {HB(3,5-Me 2 pz) 3 CpZr(OMe) 2 } is used instead of catalyst C2. 16 g of a polymer is obtained. The catalytic activity of catalyst C6 is 1,760 kg/g of Zr per hour. Example 7 Synthesis of catalyst C7 n-Butyltris(3,5-dimethylpyrazolyl)boratocyclopentadienylzirconium dichloride {nBu-B(3,5-Me 2 pz) 3 CpZrCl 2 } is synthesized according to the procedure described in Example 2. n-Butyltris(3,5-dimethylpyrazolyl)boratozirconium trichloride as a starting material is synthesized according to the method described in "Inorganic Chemistry", page 840 (1982). nBu-B(3,5-Me 2 PZ) 3 CpZrCl 2 is synthesized from the starting material and cyclopentadienyllithium in ice-cooled diethyl ether. Catalyst C7 is obtained through filtration and recrystallization. Polymerization reaction Substantially the same polymerization procedure as described in Example 2 is repeated except that a 3 ml toluene solution containing 0.1 µmole of catalyst C7, {nBu-B(3,5-Me 2 pz) 3 CpZrCl 2 } is used instead of the catalyst C2. 22 g of a polymer is obtained. The catalytic activity of catalyst C7 is 2,420 kg/g of Zr per hour. Example 8 Synthesis of catalyst D1 Hydrotrispyrazolylboratocyclopentadienyltitanium dichloride {HB(pz) 3 CpTiCl 2 } is synthesized according to the method described in J. Organometallic Chemistry, Vol. 102, page 167 (1975). Polymerization reaction Substantially the same polymerization procedure as described in Example 2 is repeated except that a 3 ml toluene solution containing 0.5 µmole of catalyst D1, HB(pz) 3 CpTiCl 2 is used instead of catalyst C2. 2.9 g of a polymer is obtained. The catalytic activity of catalyst D1 is 121 kg/g of Ti per hour. Example 9 Synthesis of catalyst E1 Hydrotrispyrazolylboratocyclopentadienylhafnium dichloride {HB(pz) 3 CpHfCl 2 } is synthesized according to the method described in J. Chem. Soc. Dalton Trans., page 603 (1991). Polymerization reaction Substantially the same polymerization procedure as described in Example 2 is repeated except that a 3 ml toluene suspension containing 0.5 µmole of catalyst E1, {HB(pz) 3 CpHfCl 2 } is used instead of catalyst C2. 9.0 g of a polymer is obtained. The catalytic activity of catalyst El is 101 kg/g of Hf per hour. Polymerization of propylene Example 10 Polymerization reaction 0.4 liter of dehydrated and deoxygenated liquid propylene is charged in a 1.6-liter autoclave evacuated and replaced with nitrogen gas. Subsequently, 1.4 ml (4.0 mmoles in terms of the amount of aluminum) of a toluene solution of methylaluminoxane (PMAO; containing 2.92 moles of aluminum/liter of the toluene solution) (manufactured and sold by Tosoh Akzo Corp., Japan) is charged in the autoclave, together with 0.1 liter of the liquid propylene. Finally, a 3 ml toluene suspension containing catalyst C1, {HB(pz) 3 CpZrCl 2 } (1.0 µmole) is charged, together with 0.1 liter of the liquid propylene in the autoclave. A polymerization reaction is allowed to proceed for 1 hour, while the temperature of the inside of the autoclave is maintained at 50 °C. 7.4 g of a jellylike polymer is obtained. The catalytic activity of catalyst C1 is 81.3 kg/g of Zr per hour. Example 11 Polymerization reaction Substantially the same polymerization procedure as described in Example 10 is repeated except that a 3 ml toluene suspension containing 1.0 µmole of catalyst C2, {HB(3,5-Me 2 pz) 3 CpZrCl 2 } is used instead of the catalyst C1. 18.0 g of a jellylike polymer is obtained. The catalytic activity of catalyst C2 is 198 kg/g of Zr per hour. [Copolymerization of ethylene and 1-hexene] Examples 12 to 17 Copolymerization reaction In a 1.6-liter autoclave evacuated and replaced with nitrogen gas are charged dehydrated and deoxygenated toluene and 1-hexene so that the total volume of toluene and 1-hexene is 800 ml (The volume of 1-hexene charged is indicated in Table 1). The autoclave is connected at a top thereof to a gas feed line and containers 1 to 3 which have been, respectively, charged with a toluene solution of a catalyst (1 µmole/3 ml) indicated in Table 1 in an amount indicated in Table 1, auxiliary catalyst MMAO also in an amount indicated in Table 1, and methanol. Each of containers 1 to 3 has a valve at a top and a bottom thereof individually, and each of containers 1 and 2 is connected to a toluene tank by means of a pipe through a pump. Then, ethylene gas is introduced into the autoclave through the gas feed line under a pressure of 10 kg/cm 2 G, while maintaining the internal temperature of the autoclave at 70 °C. A total pressure of the autoclave becomes about 11.5 kg/cm 2 G, including solvent pressure. 50 ml of toluene is fed from the tank to container 2 by means of the pump, and the top and bottom valves of container 2 are opened simultaneously, to thereby introduce auxiliary catalyst MMAO into the autoclave with toluene. Then, 50 ml of toluene is also fed from the tank to container 1 by means of the pump, and the top and bottom valves of container 1 are opened simultaneously, to thereby introduce the catalyst into the autoclave with toluene. Thereafter, a polymerization reaction is allowed to proceed for 1 hour, while the total pressure of the autoclave is maintained constantly by supplying ethylene gas and controlling the secondary pressure of a reducing valve connected to the autoclave. 10 ml of methanol is introduced in the autoclave, to thereby terminate the reaction. The amounts of a monomer and catalyst, reaction conditions, and yield and properties of the obtained copolymer are shown in Table 1. 5, 30 and 60 minutes after initiation of the copolymerization reaction, the rates of absorption of ethylene in Example 26 are 0.014 mole/min, 0.016 mole/min and 0.018 mole/min, respectively. Any lowering in absorption rate is not observed. From the results of Example 17, it is understood that the catalyst of the present invention exhibits high polymerization activity even if the molar ratio of aluminum to zirconium is 100. Comparative Example 4 Substantially the same polymerization reaction as described in Example 12 is repeated except that a comparative catalyst b, dicyclopentadienylzirconium dichloride {Cp 2 ZrCl 2 } is used instead of the catalyst C1. The absorption rate of ethylene is lowered, i.e., 0.052 mole/min, 0.015 mole/min, and 0.010 mole/min, respectively, 5, 30 and 60 minutes after initiation of the polymerization reaction. [Polymerization of styrene] Examples 18 to 20 Synthesis of catalyst D2 Hydrotrispyrazolylboratocyclopentadienyltitanium dimethyl {HB(pz) 3 CpTiMe 2 } is synthesized as follows. In the same apparatus as used in Example 5 for synthesizing catalyst C5 are charged 10 mmoles of the catalyst D1 and 50 ml of diethyl ether cooled at -78 °C. Subsequently, thereto dropwise added is 30 ml of 1 M diethyl ether solution of methyllithium over a period of 1 hour. A formed solid is filtered off to obtain a filtrate. The obtained filtrate is condensed to 10 ml and then, thereto added is dried pentane to obtain a white precipitate. The precipitate is separated by filtration, followed by drying to obtain a product. Synthesis of catalyst D3 Hydrotrispyrazolylboratocyclopentadienyltitanium dimethoxide {HB(pz) 3 CpTi(OMe) 2 } is synthesized as follows. In the same apparatus as used in Example 5 for synthesizing catalyst C5 are charged 10 mmoles of the catalyst D1 and 50 ml of diethyl ether cooled at -78 °C. Subsequently, thereto dropwise added is 30 ml of 1 M diethyl ether solution of methoxylithium over a period of 1 hour to obtain a mixture. The obtained mixture is further stirred for 24 hours. A formed solid is filtered off to obtain a filtrate. The obtained filtrate is condensed to 10 ml and then, thereto added is dried pentane to obtain a white precipitate. The precipitate is separated by filtration, followed by drying to obtain a product. Polymerization reaction of styrene In a 1.6-liter autoclave evacuated and replaced with nitrogen gas are charged 300 ml of dehydrated and deoxygenated toluene and 300 ml of stylene obtained by vacuum distillation. The autoclave is connected at a top thereof to containers 1 to 3 which have been, respectively, charged with a toluene solution of catalyst (1 µmole/3 ml) indicated in Table 2 in an amount indicated in Table 2, auxiliary catalyst MMAO also in an amount indicated in Table 2, and methanol. Each of containers 1 to 3 has a valve at a top and a bottom thereof, and each of containers 1 and 2 is connected to a toluene tank by means of a pipe through a pump. 50 ml of toluene is fed from the tank to container 2 by means of the pump, and the top and bottom valves of container 2 are opened simultaneously, to thereby introduce auxiliary catalyst MMAO into the autoclave with toluene. Then, 50 ml of toluene is also fed from the tank to container 1 by means of the pump, and the top and bottom valves of container 1 are opened simultaneously, to thereby introduce catalyst indicated in Table 2 into the autoclave with toluene. Thereafter, a polymerization reaction is allowed to proceed for 2 hours. 10 ml of methanol is introduced into the autoclave, to thereby terminate the reaction. Results of Examples 18 to 20 are shown in Table 2. Example No. Catalyst MMAO mmol Polymer obtained MEK extraction residue % Melting point °C Type µmol g kg/gZrhr 18 D1 10.0 4.0 104.3 108.6 98 273 19 D2 10.0 4.0 90.8 94.6 96 264 20 D3 7.0 3.0 121.3 180.5 98 271 [Addition of hydrogen gas in polymerization reaction system] Examples 21 to 23 760 ml of dehydrated and deoxygenated toluene and 40 ml of dehydrated and deoxygenated toluene are charged in a 1.6-liter autoclave evacuated and replaced with nitrogen gas. The autoclave is connected at a top thereof to a gas feed line which has a quantitative pipe at an intermediate portion thereof, and containers 1 to 3 which have been, respectively, charged with a 3 ml toluene solution containing 0.1 µmole of catalyst C1 {HB(pz) 3 CpZrCl 2 }, 0.18 ml (0.5 mmole in terms of the amount of aluminium) of toluene solution of PMAO, and methanol. Each of containers 1 to 3 has a valve at a top and a bottom thereof, and each of containers 1 and 2 is connected to a toluene tank by means of a pipe through a pump. Under atmospheric pressure, hydrogen gas is introduced into the quantitative pipe via the gas feed line to thereby quantitate the hydrogen gas. Then, ethylene gas is introduced into the autoclave through the gas feed line and the quantitative pipe under a pressure of 10 kg/cm 2 G, together with the quantitated hydrogen gas, while maintaining the internal temperature of the autoclave at 80 °C. A total pressure of the autoclave becomes about 10.4 kg/cm 2 G, including a solvent pressure. 50 ml of toluene is fed from the tank to container 2 by means of the pump, and the top and bottom valves of container 2 are opened simultaneously, to thereby introduce auxiliary catalyst PMAO into the autoclave with toluene. Then, 50 ml of toluene is also fed from the tank to container 1 by means of the pump, and the top and bottom valves of container 1 are opened simultaneously, to thereby introduce catalyst C1 into the autoclave with toluene. Thereafter, a polymerization reaction is allowed to proceed for 1 hour while the total pressure of the autoclave is maintained constantly by supplying ethylene gas. 10 ml of methanol is introduced into the autoclave, to thereby terminate the reaction. Comparative Examples 5 to 7 In each of Comparative Examples 5 to 7, substantially the same procedure as in Examples 21 to 23 is repeated except that comparative catalyst b {Cp 2 ZrCl 2 } is used instead of catalyst C1 and the amount of hydrogen gas to be introduced into the autoclave is changed. Results of Examples 21 to 23 and Comparative Examples 5 to 7 are shown in Table 3. Example and Comparative Example Nos. Hydrogen amount (Nml ) HMI (g/10 min) Molecular weight (Mw) Molecular weight distribution (Mw/Mn) Example 21 0 0.2 880400 2.80 Example 22 75 10.5 381000 3.08 Example 23 188 60.6 169000 2.82 Comparative Example 5 0 0.4 515000 2.36 Comparative Example 6 5 2.1 387000 2.82 Comparative Example 7 40 359.00 94000 3.28 As is apparent from the above, when the catalyst of the present invention is used (Examples 21 to 23), the molecular weight of the polymer can be easily controlled by adding hydrogen gas in the polymerization reaction, while when comparative catalyst b (dicyclopentadienylzirconium dichloride) is used (Comparative Examples 5 to 7), the molecular weight of the polymer is markedly decreased by adding a very small amount of hydrogen gas in the polymerization reaction. This means that by the use of comparative catalyst b, molecular weight of a polymer can hardly be controlled. [Solution polymerization] Example 24 700 ml of dehydrated and deoxygenated toluene and 100 ml of dehydrated and deoxygenated 1-hexene are charged in a 1.6-liter autoclave evacuated and replaced with nitrogen gas. The autoclave is connected at a top thereof to a gas feed line and containers 1 to 3 which have been, respectively, charged with a 3 ml toluene solution containing 2 µmole of catalyst C1 {HB(pz) 3 CpZrCl 2 }, 0.5 ml (1.0 mmole in terms of the amount of aluminum) of toluene solution of MMAO, and methanol. Each of containers 1 to 3 has a valve at a top and a bottom thereof, and each of containers 1 and 2 is connected to a toluene tank by means of a pipe through a pump. Ethylene gas is introduced into the autoclave through the gas feed line while maintaining the internal temperature of the autoclave at 110 °C. A total pressure of the autoclave becomes about 13 kg/cm 2 G, including a solvent pressure. 50 ml of toluene is fed from the tank to container 2 by means of the pump, and the top and bottom valves of container 2 are opened simultaneously, to thereby introduce auxiliary catalyst MMAO into the autoclave with toluene. Then, 50 ml of toluene is also fed from the tank to container 1 by means of the pump, and the top and bottom valves of container 1 are opened simultaneously, to thereby introduce catalyst C1 into the autoclave with toluene. Thereafter, a polymerization reaction is allowed to proceed for 30 minutes, while the total pressure of the autoclave is maintained constantly by supplying ethylene gas and controlling the secondary pressure of a reducing valve connected to the autoclave. The secondary pressure of the reducing valve is monitored to measure the absorption rate of the ethylene gas. 10 ml of methanol is introduced into the autoclave, to thereby terminate the reaction. 47.2 g of a polymer is obtained. It is found that a catalytic activity of catalyst C1 is 518 kg/g of Zr per hour, and the absorption rate of ethylene gas 5 minutes after initiation of the reaction are substantially not changed from that of ethylene gas 30 minutes after initiation of the reaction. [Preliminary polymerization] Example 25 Preparation of suspension F1 of solid components Under nitrogen atmosphere, a 200-milliliter autoclave is charged with 1 g of silica gel (manufactured and sold by Fuji-Davison Chemical, Ltd., Japan) which has been calcinated at 300 °C for 4 hours under nitrogen atmosphere. The calcinated silica gel is suspended in 43 ml of toluene in the autoclave to thereby obtain a suspension. To the obtained suspension are added 21 mmoles of PMAO (in terms of the amount of aluminum) and 2.0 mmoles of triisobutylaluminum (in terms of the amount of aluminum) as auxiliary catalysts, to thereby obtain a suspension. The obtained suspension is stirred at room temperature for 2 hours and then, decanted to thereby obtain solid components. The obtained solid components are washed with toluene 3 times. The washed solid components are suspended in 10 ml of toluene. The resultant suspension is designated as F1. Preliminary polymerization 84 µmoles of catalyst C1 is added to suspension F1, and preliminary polymerization is allowed to proceed at room temperature for 30 minutes. 9 g of a polymer is obtained. It is found that a catalytic activity of catalyst C1 is 2300 g/g of Zr per hour. The obtained polymer is designated as catalyst G1. Polymerization 760 ml of dehydrated and deoxygenated toluene and 40 ml of dehydrated and deoxygenated 1-hexene are charged in a 1.6-liter autoclave evacuated and replaced with nitrogen gas. The autoclave is connected at a top thereof to a gas feed line and containers 1 to 3 which have been, respectively, charged with a 17 ml toluene solution containing 4.68 µmole of catalyst G1, a 3 ml toluene solution containing 0.5 mmole (in terms of the amount of aluminum) of triisobutylaluminium as an auxiliary catalyst, and methanol. Each of containers 1 to 3 has a valve at a top and a bottom thereof, and each of containers 1 and 2 is connected to a toluene tank by means of a pipe through a pump. Ethylene gas is introduced into the autoclave through the gas feed line under a pressure of 7 kg/cm 2 G while maintaining the internal temperature of the autoclave at 70 °C. A total pressure of the autoclave becomes about 8.5 kg/cm 2 G, including a solvent pressure. 50 ml of toluene is fed from the tank to container 2 by means of the pump, and the top and bottom valves of container 2 are opened simultaneously, to thereby introduce triisobutylaluminum as an auxiliary catalyst into the autoclave with toluene. Then, 50 ml of toluene is also fed from the tank to container 1 by means of the pump, and the top and bottom valves of container 1 are opened simultaneously, to thereby introduce catalyst G1 into the autoclave with toluene. Thereafter, a polymerization reaction is allowed to proceed for 1 hour while the total pressure of the autoclave is maintained constantly by supplying ethylene gas and controlling the secondary pressure of a reducing valve connected to the autoclave. 10 ml of methanol is introduced into the autoclave, to thereby terminate the reaction. 97 g of a polymer is obtained. It is found that a catalytic activity of catalyst G1 is 227 kg/g of Zr per hour. The bulk density of the polymer is 0.15 g/cm 3 , and the HMI of the polymer is 3.5 g/10 minutes. [Stable non-coordinating auxiliary catalyst] Example 26 Polymerization A 1.6-liter autoclave, which has been evacuated and replaced with nitrogen gas, is provided. The autoclave is connected at a top thereof to containers 1 to 3 which have been, respectively, charged with a 10 ml toluene solution containing 0.01 mmole of triisobutylaluminium as an auxiliary catalyst (in terms of the amount of aluminium), a 3 ml toluene solution containing 0.001 mmole of dimethylaniliniumtetra(pentafluorophenyl)borate as another auxiliary catalyst, and methanol. Each of containers 1 to 3 has a valve at a top and a bottom thereof, and each of containers 1 and 2 is connected to a liquid propylene tank by means of a pipe through a pump. 0.4 liter of liquid propylene is fed from the tank to container 1 by means of the pump, and the top and bottom valves of container 1 are opened simultaneously, to thereby introduce triisobutylaluminium as an auxiliary catalyst into the autoclave with liquid propylene. After the introduction of triisobutylaluminium, a 3 ml toluene solution containing 1.0 µmole of catalyst C5 {HB(3,5-Me 2 pz) 3 CpZr(CH 2 Ph) 2 } is charged in container 1. Then, 0.1 liter of liquid propylene is fed from the tank to container 2 by means of the pump, and the top and bottom valves of container 2 are opened simultaneously, to thereby introduce dimethylaniliniumtetra(pentafluorophenyl)borate as another auxiliary catalyst into the autoclave with liquid propylene. Then, 0.1 liter of liquid propylene is also fed from the tank to container 1 by means of the pump, and the top and bottom valves of container 1 are opened simultaneously, to thereby introduce catalyst C5 into the autoclave with toluene. Thereafter, a polymerization reaction is allowed to proceed for 1 hour while the total pressure of the autoclave is maintained constantly by supplying ethylene gas. 10 ml of methanol is introduced into the autoclave, to thereby terminate the reaction. 6.6 g of a jellylike polymer is obtained. It is found that a catalytic activity of catalyst C5 is 72.6 kg/g of Zr per hour.

Claims: An olefin polymerization catalyst comprising at least one transition metal compound selected from compounds of formulae I and II: wherein: M is a transition metal selected from the group consisting of metals of Groups IIIA including the lanthanide series, IVA, VA, VIA, VIIA and VIII of the Periodic Table of the Elements, X is an anionic ligand, n is an integer represented by formula G-2 in which G is the Group number of the Group of the Periodic Table to which said transition metal belongs, and L 1 and L 2 are ligands defined below, wherein a bridge bond is optionally formed between L 1 and L 2 ; and wherein: M, X, n, L 1 and L 2 are as defined for formula (I), and J is a non-coordinating anion; said ligand L 1 being a trispyrazolyl tridentate ligand represented by formula III: wherein: A is a carbon atom, or a boron atom substituted with a substituent selected from the group consisting of: a hydrogen atom, a saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 -C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group; each of Z 1 , Z 2 and Z 3 independently represents a pyrazolyl group represented by formula IV: wherein: each of R 3 , R 4 and R 5 independently represents: a hydrogen atom, a saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group which is unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group or at least one halogen atom, a C 6 - C 20 aromatic hydrocarbon group which is unsubstituted or substituted with at least one C 1 -C 10 alkyl group or at least one halogen atom, an oxy group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a thio group which is substituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group unsubstituted or substituted with at least one C 6 - C 14 aromatic hydrocarbon group, or which is substituted with a C 6 - C 20 aromatic hydrocarbon group unsubstituted or substituted with at least one C 1 - C 10 alkyl group, a silyl group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, a siloxy group which is unsubstituted or substituted with at least one saturated or unsaturated C 1 -C 20 aliphatic hydrocarbon group, at least one C 6 - C 20 aromatic hydrocarbon group or at least one halogen atom, an amino group which is N,N-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, and a phosphino group which is P,P-disubstituted with a saturated or unsaturated C 1 - C 20 aliphatic hydrocarbon group or a C 6 - C 20 aromatic hydrocarbon group, wherein a bridge bond is optionally formed between R 3 and R 4 or between R 3 and R 5 , and said ligand L 2 being an alkapolyenyl ligand having a σ-bond and two or more π-bonds. The catalyst according to claim 1, wherein said transition metal of each of formulae I and II is from Group IVA of the Periodic Table. The catalyst according to claim 2, wherein said transition metal is selected from the group consisting of Ti, Zr and Hf. The catalyst according to claim 1, wherein said ligand L 2 is an alkadienyl ligand. The catalyst according to claim 1 or 4, wherein said ligand L 1 represented by formula III is hydrotris(3,5-dimethylpyrazolyl)borate. The catalyst according to claim 1 or 4, wherein said ligand L 1 represented by formula III is hydrotris(pyrazolyl)borate. The catalyst according to any one of claims 1 to 6, further comprising an auxiliary catalyst comprised of an alkylaluminoxane.

Inventors: AOKI TOSHIYA, KANESHIMA TOKITAKA, AOKI, TOSHIYA, KANESHIMA, TOKITAKA
Applicants: ASAHI CHEMICAL IND, ASAHI KASEI KOGYO KABUSHIKI KAISHA
Application year: 1994
Main classification: C08F4
IPC codes: C08F4, C08F210, C08F10